Thermally sensitive control switch



ct. 31, 1939. s MCPHERSQN, JR @9,178,485

THERMALLY SENSITIVE CONTROL SWITCH Filed OC.. 31, 1938 ATTORNEYS Patented Oct. 31, 1939 Unirse stares PAT EN T OF F l C E 4 Claims;

This` invention relates .to improvements in thermally controlled switches'and is particularly concerned withy a new and improved control A switch sensitive to variation both in tempera- 5'` ture and humidity. y ,v

Control switches of) thentype heretoforeused have beenvsensitive to variations in temperature or in humidity: it is an object of the present inventionto `provide a switchrsensitive to variations both in humidity and in temperature whereby air conditioning apparatus including a heater, a cooler, anda humidifier can be substantially automatically controlled.

Another object of the present invention is to lprovidewa new and improved psychrometrically controlled switch whichV can be adjusted to function for any preselected atmospheric tempera-tures andrdegrees of relative humidity.

Another object of thepresent invention is to provide a novel psyohrometrically controlled switch of the type aforesaid which comprises relatively Nfew parts, all of which are simple of construction .and can be manufactured from .y relativelyvcheap materials, whereby manufacture 2li/of the device by massv production is at least largely promoted, and the necessity of repair because of break-down during use is minimized.

YAnadvantage of the novel switch according tohlthe instant invention is the relatively few "moving Aparts thereof which result in long, useful life of the device without necessity of replacme Worn parte i noteworthy feature of the switch, according to this invention, is its simplicity of construction "and therelatively small number of elements comprising the device whereby it is especially suited the requirements of mass production.

Other objects, advantages and features of the novel psychrometrically controlled switch ac- I cording to the present invention will be apparent to those skilled inthe art during the course of the following description.

Regarded in certain of its broader aspects the Hprese-nt invention comprises a pair of mounted, thermally sensitive, elements arranged whereby variation in temperature of said elements results in movement of ends thereof in opposite direction, means'whereby one ,of said elements is sensitive to variations in humidity in addi- Mtion` togvariations in temperature, a conductor member connectedthrough said ends of said elements and movable therewith, and a series of electrical Contact elements cooperating with said Coil'llitff whereby- Variations in atmospheric l`temperature and/or humidity result in establishment of electrical connection, successively, between the conductor and said contact elements.

In order to Afacilitate a fuller and more complete understanding of the matter of the present invention, `a specic embodiment thereof will 5 be hereinafter described, it being clearly understood, however, that this specic embodiment is given solely by way of example and is non-limitative upon the scope of the present invention, except as is expressed in the subjoined claims. 10

Referring then to the drawing:

Figure 1 is substantially'a front elevational view of the presently preferred embodiment of the instant invention, parts being broken away for clearness of illustration and the electrical 15 circuitsrbeing shown in lschematic form.

Figure 2 Aand Figure 3 are, respectively, front elevational views of the device illustrated in Figure l showingrthe electrical conductor elements thereof in different positions, the former showing the conductor in position of maximum slack, and the latter showing the conductor in substantially taut condition.

Referringv nowto the drawing it' will be noted that the illustrated embodiment of this invention comprises a'support I preferably a vertically positioned, essentially flat plate carrying a pair of projecting rotatable but normally frictionally held posts II and I2 upon which are mounted the thermally sensitive elements I3 and i4, substantially'as shown. It is to be noted that the thermally sensitive elements I3` and I4 comprise spirally curved end 'portions Ita` and Ida, respectively, the spirals being wound in opposite direction. It is to be understood that the thermally sensitive elements I3 and I4 are of any conventional type such as composite elements now commonly in use which comprise united membershaving different coeiicients of expansion whereby variation in temperature of the structure results in distortion ofthe shape thereof. It is to be noted that the thermally sen-l sitive element M is provided with a covering Mb of relatively absorbent material communicating by means of a wick |40 with a fluid reservoir lld. 1n this manner evaporation of fluid from the coating lllb alters the temperature of the element I/l due to the absorption of heat by evaporation of fluid.

The distal free ends l3b and I4e of the thermally sensitive members IS'and I4 respectively carry, 'disposed' in a catenar'y therebetween, an electrically conductive element I5, said element being formed of exible material whereby movement of the free ends of the thermally sensitive elements result in vertical motion of intermediate portions of said conductor element.

It will be apparent to those skilled in the art that the free end portion |3b of the element I3 will move, in the illustrated embodiment of the present invention, in a counterclockwise direction as the temperature rises, and conversely that the element I4 will operate whereby its free end portion I4e will move in a clockwise direction as the temperature thereof increases. It is to be noted that the motion of the end portion I4e of the element I4 is not dependent solely upon Variation in temperature but instead upon variations both in temperature and humidity.

A pair oi guide elements I6 and I'I mounted in spaced parallelism upon the support I0 by fastening means I3, define a vertically extending channel for slidingly receiving a plate-like member I9 carrying contact elements 2U, 2|, and 22 thereon substantially as shown. It is to be noted that the member I9 is vertically adjustable by means including a rack 23 associated with said member and engaging with a pinion gear 24 whereby vertical motion can be imparted to said member I9 by rotation of said gear 24. It is particularly to be understood that the iiexible electrical conductor I5, as it moves from relatively taut to relatively slack position wipes across, successively, the contact elements 20, 2|, and 22 hereinbefore referred to.

Inuse of the device, electrical circuit is established including a power source 26 electrically connected to the conductor I 5 and relay switches connected to said power source through means including the contact elements 20, 2|, and 22, whereby said relays can be operated by wiping of the conductor` member I5 across said contact elements. It is to be understood of course in this connection that insulation can be provided upon the device for electrically isolating the contact .elements 20, 2|, and 22, relative both to each other and to the wiping conductor member I5, these features being conventional in the art and not illustrated.

For a further understanding of the instant invention the figures of the drawing can be considered as illustrations of the relative position of elements of the device under different atmospheric conditions. For instance, in Figure 1 the catenary conductor is shown in an intermediate y position in contact with the` contact element 2|.

Under these conditions it may be assumed that the apparent variation in temperature between the elements I3 and I4 is five degrees C. That is to say, evaporation oi moisture from the coating |413 of the member I4 results in lowering the temperature of said element by iive degrees. Referring now to Figure 2 it will be noted that the catenary conductor I5isillustrated in contact with the contact element 22, that is to say that the conductor is in the maximum slack position. This poisition corresponds to the maximum difference in apparent temperature of the thermally sensitive elements I3 and I4 which may be assumed in this instance to be 10 degrees. Another position of the catenary conductor I 5 is illustrated in Figure 3 and corresponds to relatively taut condition of said conductor. It is to be noted that the conductor, when so disposed, is in contact with the contact element 20. It is particularly to be noted in respect to this figure that although the apparent temperature difference between the thermally sensitive elements I3 and I4 is but ve degrees as was noted in regard to Figure 1 hereinbefore referred to, the temperature of each of the thermally sensitive elements is increased by ten degrees, whereby the end parts |311` and I4e respectively of said elements, are disposed at the maximum distance from each other limited by the catenary conductor.

Having thus described the matter of the present invention, what is desired to secure by Letters Patent is expressed in the following claims.

I claim:

1. A psychrometrically controlled switch comprising a iirst and a second thermal-sensitive element arranged whereby, in use, moving ends of said elements travel in opposite directions; said second element carrying a moisture laden cover whereby variations in humidity alter the temperature of said element; an electrical conductor mounted on the moving ends of said elements; and a series of electrically isolated contact elements wiped by said conductor during motion of said end of said thermal-sensitive elements, whereby variations in surrounding atmospheric temperature and, upon occasion, humidity, cause said conductor to successively wipe the contact elements and establish electrical contact therewith.

2. A psychrometrically controlled switch cornprising a first and second thermal-sensitive element arranged whereby, in use, moving ends of said elements travel in opposite directions; said second element carrying a moisture laden cover whereby variations in humidity alter the temperature of said element; an electrical conductor mounted on the moving ends of said elements; a vertical adjustable sliding plate, and a series of electrically isolated contact elements mounted on said plate and wiped by said conductor during motion of said ends of said thermal-sensitive elements whereby variations in surrounding atmospheric temperature and, upon occasion, humidity, cause said conductor to successively wipe said contact elements and establish electrical contact therewith.

3. A psychrometrically controlled switch coinprising a support; a rst and a second thermalsensitive element mounted on said support; said rst element being mounted at a place distal re1- ative to one end thereof whereby variation in temperature of said element results in movement of said end; said second element being mounted similarly to said iirst element but in a manner whereby, in use, the moving ends of said elements travel in opposite directions; said second element carrying a moisture-laden cover whereby variations in humidity alter the temperature of said element; a flexible electrical conductor mounted on and disposed in a catenary between the moving ends of said iirst and said second elements; and a series of electrically isolated contact-elements wiped by said conductor during motion of said ends of said thermal-sensitive elements whereby variations in surrounding atmospheric temperature and, upon occasion, humidity, cause said conductor to successively wipe said contact elements and establish electrical contact therewith.

4. A psychrometrically controlled switch comprising a support; a iirst and a second thermalsensitive element mounted on said support; said rst element being mounted at a place distal relative to one end thereof whereby variation in temperature of said element results in movement of said end; said second element being mounted similarly to said first element but in a manner whereby, in use, the moving ends of said elements travel in opposite directions; said second element motion of said ends of said thermal-sensitive elements whereby variations in surrounding atmospheric temperature and, upon occasion, humidity, cause said conductor to successively wipe said Contact elements and establish electrical Contact 5 therewith.

SAMUEL G. MCPI-IERSON, JR. 

